NVDA Add-ons 2: types of add-ons

Hi,

Let’s continue with add-on development…

Last time, we talked about preparing for add-on development. We left off at what kinds of add-ons are available. Let’s go over types of add-ons available.

Add-ons can be divided into three categories: global plug-ins, app modules and drivers. A global plug-in adds additional functionality for NVDA, such as OCR capability, support for controls seen in multiple apps and so on. Examples are OCR, emoticon announcements and so on. In contrast, an app module provides support for an app, with examples being GoldWave, Outlook and so forth. Lastly, drivers provide support for speech synthesizers and braille displays.

Each add-on type inherits from a base module. A typical initial code looks like this:

import globalPluginHandler/appModuleHandler/handlers for drivers

Then you would write:

Class AppModule(appModuleHandler.AppModule)/GlobalPlugin(globalPluginHandler.GlobalPlugin):

               Code…

I will not cover drivers here as they require extensive knowledge of how synthesizers/braille displays work (and I haven’t written any). We’ll start with similarities between global plugin and app modules, and we’ll dive into differences between them.